Fluid-pressure-operated means for controlling apparatus at a distance



July 3, 1945. E. DonsoN FLUID PRESSURE OPERATED MEANS FOR CONTROLLING APPARATUS AT A DISTANCE Filed April 2,2, -1944 N y A# i w A@ w mm l m. A L A if AA Rw. A mw A h. A A l www mw A o o A.. A .m A wN n4 m l m. N VN YQ/. mw m. NW @N A .f A A AAA, m A N A xv n l @www ANA.

,JA QT A g Patented July 3,1945

nutren sV iliillillii-WRJESSEIRE-OPEIM'llEDv MEANS FOR CNTRULDJG APPARATUS AT A DIS- TANCE Edward Dodson, Puriton, near Bridgwater,

l England Application April 22, 194i, Serial No. 532,31'.

En Great Britain `lanuary 6, i944 ,'1' creams. (ci. 3oz- 54) This invention relates to a sender unit for a hydraulic remote control system of the kind,

described for example in United StatesApplicaposed at one end to the pressure of the outlet and at the other end to the pressure of a balancing spring and` operable, by movement in opposite directionsfrom a neutral position, to place the outlet in communication with the inlet port and with the exhaust port respectively, and an operating member for varying the load ,on the balancing spring and thereby displacing the valve in the direction to produce a counter-balancing change of pressure at the outlet.

It is desirable to use very high hydraulic pressures, i. e., pressures up to 1000 lbs. per sq. in. or higher on aircraft because of the resultant saving in weight and size of the conduits and of the jacks, and other mechanisms to .be operated by the uid pressure. If, however, pressure fluid tapped fromsuch a high pressure source is fed to the inlet port of a sender unit of the above type difficulties are to be' expected from the phenomenon known as hydraulic lock.

While a balanced piston valve may be perfectly free when exposed to these high pressures and kept moving, if it is allowed to remain stationary for a short period it requires a great eort to move it again. It appears as if the valve does not remain central in its cylinder, and that when it gets to one side the whole ofthe pressure is exerted in forcing it against that side; and curiously when the pressure is relieved it takes an appreciable time before the valve becomes free again.

With the objectv of avoiding diiiiculties due to sticking-of the valve, the invention-provides a sender unit of the above kind, in which the inlet port is subject to reduced pressure' derived from the high4 pressure by means of a pressurereducing valve arranged to' maintain the pressure at the inlet port in excess of that at the outlet by a predetermined nxed amount. Thus in a typical case the supply pressure may pressure at a value from 65-200 lbs/sq. in., according to the position of the operating member, and the reduced pressure 50 lbs/sq. in. in excess of the prevailing signal line pressure. As hereinafter explained, there will be transitory variations in the pressure difference between the inlet be etween 300 and 1000 lbs/sq. in., the signal line port and the outlet while the sender unit is operating to change the pressure in the signal line to correspond with an adjustment in the position of the operating member. By the expression fixed amoun I mean that the pressure difference between the inlet port and the outlet will be a constant one under steady conditions for all position of the operating member.

In one arrangement according to the invention, the sender unit comprises a high pressure inlet, a conduit connecting the inlet and the inlet port in the cylinder, a non-return valve controlling communication between the inlet and the conduit, and a. spring-loaded piston exposed at the spring loaded end to the outlet 4pressure and at the other end to the pressure in the conduit, said piston being arranged to open the non-return valve when the difference between the conduit and outlet pressures falls below the pressure of said spring.

rlhe operating member may conveniently be constituted by a pivoted lever and it is preferred to provide in the conduit a plunger linked to the lever and arranged to balance the reaction on the leverof. the pressure exerted by the balancing spring.

One' specific embodiment of the invention will ynow be described in greater detail, by way of example, with reierence to the accompanying drawing, in whichl Fig. 1 is a diagrammatic showing of the layout of a hydraulic remote control system-for actuating the iiying control of an aircraft, I

Fig. 2 is a vertical section through the sender unit.

rihe hydraulic remote control system shown in Fig l, comprises a reservoir l0 to contain oil, a pumpll serving to feed oil via a pipe :i2 to a sender unit l3,a duplicatedv signal line i4 leading from the sender unit (which is in the cockpitY and operated by a pilots lever I5) to a receiver unit lli, pipes I'Land I8 leading respectively from the receiver unit to opposite ends of a hydraulic jack i9, and pipes 20, 2l serving respectively for return of. the oil from the sender ,and receiver units to the tank. 'Iheconstruction of the receiver unit is f ully described in 1r r copending U. S. application Serial No1 532,311. It operates, by hydraulic pressure received through the duplicated' pipe line I4 to adjust theposition of the jack i9, and therefore of a-lever 22 for actuating the ying control (not shown) to conform with the position of the pilots lever l5. At each end of the duplicated signal line I4 is a cut-out valve 23, the cutout valve 23 associated with the sender unit being 23, above referred to. This ing in which is formed a cylinder 24. This communicates at its frontend with an inlet 25 communicating with the high pressure hydraulic supply line I2. In the inlet 25 is mounted a non- .return valve 26 which is normally held on its l seating 2l by a spring 28. Immediately to the rear of the inlet, and at the forward end of the cylinder 24, is a hollow piston 29, containing a spring 30 which urges the piston/forwards. (i. e., to'the left in Fig. 2). To the rear of the piston 29 is a piston valve 3| of the twoland type controlling an inlet port 32, an exhaust port 33, and giving access to an outlet 34 from its waisted with the return line 20 to the tank while the outlet 34 communicates with the duplicated pipe line I4 through the agency of the cut-off valve comprises a diaphragm 35, loaded at each side by a spring 31 'and carrying on4 each side a valve 38. The diaphragm normally'occupies the illustrated neutral position, but on failureof the pressure in either section of the signal line I4, the hydraulic pressure on the other side of the diaphragm will overcome th'e spring 31 and close the valve 38 controlling the ow from the outlet 34 to the af fected section of the signal line I4.

The forward land of the-pistonvalve 3| has a channel 33 in it aii'ordingcommunica'tion to the outlet 34 from the space 40 between the forward end of the piston valve 3| `and tl'ie rear end of the piston 29. Aeconduit4| connects the space 42 at the front pf the piston 29 with the inlet port 32, and ports 43 in the cylinder near the forward end oi the reducing valve communicate by conduits 44 with theoutlet 34, these ports 43 being normally closed trated.

The piston valve 3| is subjected at its rear end to the pressure of a balancing spring 45, the compression -oi which is variable by means of a plunger 45 linked by a link 4l to the pilots throttle lever I5, which is mounted on a pivot 43. A

fsecond spring 53 acts to urge the piston valve 3| rearwardly in opposition to the balancing spring 45. A balancing plunger/49, subject to the pres.-

-sure in the conduit 4|,.is coupled by a link 50 to the pilots lever- I and serves, Vas hereinafter more fully explained, to balance it reaction of the balancing spring 45.

The .piston '29 is exposed at itsleft hand end to the pressure in conduit 4| and at its right hand end to the pressure in the outlet passage 34 and to the pressure of spring 3U. These pressures. normally balance, and spring 30 is such that the 'pressure in conduit 4| exceeds by 50 vlbs/sq. in.

against the the pressure in the outlet passage 34 and signal line I4. 'I'he piston 29 and its associated spring 30 therefore operate to maintain in the conduit 4I a reduced pressure at a value 50 lbs/sq. in. in excess of that in the signal line I4. Il? the pilot moves his lever l5 to increase the compression of the'balancing. spring A45, the pistn valve 3| will move forward to open the inlet port 32, and I allow reduced pressure, from the conduit 4I to flow into the signal line I4 to increase the signal line pressure, andeflect a corresponding movement of a pressure sensitive member at the dis.l

25 that, when added to the 35 the uid displaced by this plunger.

by the piston 29 as 111 -v 2,379,692 located in the body thereof as later described. The

tant receiver unit I6 which in turn-moves the flying control accordingly through the agency of the jack I9. At the same time, the resulting fall 1n pressure in the conduit 4| enables the spring 5 30 ofthe piston 29, assisted by the pressure in l0 outlet 34, acting on the forward end of the piston `valve 3| through the channel 39, plus the pressure of spring 53, balances the pressure of the balancing spring 45, the piston valve 3| will return to its neutral position, and as soon as the pressure in the conduit 4I is again 50 lbs/sq.

in. in excess of that at the outlet 3 4, the piston 29 returns rearwardly toits original position allowing the non-return valve 26 to close.

When the pilots lever is moved to reduce the compression of the balancing spring 45, t episportion 35. The exhaust port 33 communicates ton valvel 3| moves to the rear, placing the signal line I4 in communication with the exhaust port 33. iIt returns to the'neutral position as soon as the outlet pressure has dropped to a value such pressure of the spring 53, it is again equal to the new pressureof the balancing vspring 45. The pressure in the conduit 4| would soon fall to a value once nore 50 lbs/sq. in. in excess of the outlet pressure by leakage to exhaust past the piston valve 3|.

Clockwise movement of'the pilots lever I5 about its pivot, to reduce the' signal line pressure, however involves forward movement of the balancing plunger 49 and the ports 43 serve to'get rid of This is effected by rearward movement of the piston 29, opening the ports 43 and allowing this 'uid to escape to exhaust through the conduits 44, chan- 'nel 39 and the rearwardly displaced piston valve The piston 29 returns to its normal illustrated position, in which it closesv the ports 43, whenthe reduced pressure in the conduit 4| has vdropped to a value 50 lbs. in exce'ssvof the new signal line pressure.

pressure in conduit 4| exceeds that value. This] 5 is lbecause such fluid as may leakfrom inlet port 32 to the waisted portion 35 of piston valve 3| flows to.exhaust port'33 and is replaced, when the pressure in conduit 4| tends to drop due to such leakage to less than 50 lbs./sq. in. above the signal line pressure, by opening of the ball valve 26. f

In the absence of spring Sfthe conduit pressure acting on `the plunger 49 wouldA be unable `to balance the torque exerted on the pilots lever Vthe pilots lever, because this'conduit -pressure signal line pressure, and therefore the loading 0 of the spring 45, mayhowever vary from 65-200 lbs/sq. in.,accor'ding to the position of the pilots lever. If the area of the plunger 49 and the leverage exerted by its link 50were arranged to eilect 7 a balance'when the loading of the spring 45 was lbs./sq. in. and-the conduit pressure therefore It will be noted from Fig. 2 that when piston valve 3| is in its neutral position, the waisted y is by the balancing spn'ng d5 in au positions of 115 1in/sq. in., it is clear that there would not lbs/sq. in. I obtain a perfect balance for all positions, however,` by utilising the spring. 53

which is given the same load (in this instance 50 lbs/sq. in.) as the spring '30 associated with the piston 29. In this way the load imposed on the pilots lever by the link 3l is made equal to that acting on the plunger t9, i. e., outlet pressure plus 50 lbs/sq. in. for all positions of vthe lever iii. l

The space 5d in which the balancing spring 53 4is housed is, as shown, connectedto the exhaust port 33 and therefore exposed to exhaust back pressure. The effective area. of the plunger dii is made equal to that of the piston valve 3l so that the exhaust back pressure does not destroy the balance of the operating lever. When there is any considerable exhaust back pressure,4 it of course increases the signal line pressure, together with the conduit pressure. creased counter-acting torquefrom the balancing plunger i9 which exactlyequalises the increase in thrust on the plunger d6. As Vexplained in my copendin-g U. S. application Serial No. 532,311, Vthe exhaust back pressure also acts on the rear of the sensitive piston of the receiver unit, so that changes in signal line pressure due to variations in exhaust back pressure will not affect the This gives an in-V ply and comprising a cylinder having inlet and exhaust ports and an outlet, a piston valve in the cylinder exposed at one end to the fluid pressure at the outlet and operable by movement in opposite` directions from a neutral position to place the outlet in communication with the inlet port and with the exhaust port respectively, a spring for balancing the piston valve against the pressure at the outlet and thereby urging it to the neutral position, an operating member for varying the pressure of the spring for the purpose of displacing the piston valve to raise Vor lower the pressure at the outlet, an inlet for connection to the high pressure supply, a conduit connecting said high pressure inlet with the inletport, a non-return valve controlling communication between said inlet and said conduit, a piston subjected at one end to the pressure in said conduit and at the other end to the pressure at the outlet, and a loading spring operating on the end of the reducing valve exposed to outlet pressure, .said piston operating to maintain in said conduit a reduced pressure exceeding that at the outlet by the pressure of said loading'spring, and serving to open the non-return valve when the difference between i the conduit and outlet pressures falls below'the pressure of said loading spring.

3. A sender unit as claimedl in claim 2, in which V the operating member is constituted by a pivoted position of said sensitive piston or of the iiying control operatedby the receiver unit.

There will be no danger of the piston valve ill sticking, despite the use of the high supply pressure, because the pressure on it will always be only 50 lbs. in excess of the signal line pressure,

which will, as above stated, vary 4fren-.i 65420@ lbs/sq. in. according to the position of the pilots lever It. Moreover the fluid displaced by the balancing plunger, on movement of the pilots lever lb to reduce the signal line pressure, will assist in overcoming any tendency of the piston valve 3i to stick, by exerting a positive pressure on its forward end. The balancing plunger iii exposed to conduit pressure has been found to provide a perfect balance of the pilots lever, ,which requires no appreciable eiort to move it, the balance being stabilised by the friction developed by the sealing arrangement (not shown) of the balancing piston in its cylinder.

tively, a spring for balancing the piston valve' against the pressure at the outlet and thereby urging it to the neutral position, an operating member for varying the pressure of the spring for the purpose of displacing the piston valve to raise or lower the pressure at the outlet, an inlet ior connection to the high pressure supply, and a pressurereducing valve for subjecting the inlet port to reduced pressure derived from the high pressure at the inlet, and maintaining at lever and comprising a plunger exposed to the pressure in the conduit and operatively connected to said lever, said plunger being arranged to. balance the reaction thereon of.the balancing spring.

{l} A sender unit for a hydraulic remote control system, adapted for use with a high pressure hydraulic supply and comprising a cylinder having inlet and exhaustports, and an outlet, a piston valve in the cylinder exposed at its forward end to the 'uid pressure at the outlet and at its rear endto the .exhaust port pressure, said piston valve being operable by movement in opposite directions from a neutral position to place the outlet in communication with the inlet port and with the exhaust port respectively, av balancing spring operating on the rear end of said piston valve, a pivoted operating lever for varying the pressure of said spring and thereby displacing the piston valve to vary the pressure at the outlet, an inlet at the forward end of the cylinder for connection to the high pressure supply, a nonsaid inlet port a reduced pressure which exceeds `that at the outlet by a xed amount.

2. A sender unit for a hydraulic remote control` system, adapted for use with a high pressure supreturn valve for maintaining said inlet normally closed, la conduit connecting the portion of the cylinder immediately in rear of the non-return valve to the inlet port, a piston in the cylinder located in advance of the piston valve and exposed at its forward end to thev conduitpressure and at its rear end to the outlet pressure, and a loading spring, operating on the rear end of said piston, the piston maintaining the conduit pressure in excess of the inlet pressure by :a xed amount determined by the pressure of said loading spring and serving to open the non-return valve to increase the conduit pressure, when said excess pressure falls below the pressure of said loading spring.

5. A sender unit as claimed in claim 4, comprising a second spring operating on the piston valve in `opposition to itsbalancing spring, the loading of said second spring being equal to that of the loading spring action on the piston, and a balancing plunger'exposed to the pressure in the conduit and linked to the operating lever and serving to balance, in all positions thereof, the reacticn exerted thereon by the balancing spring.

6. A sender -unit as claimed in claim 4, comp ing a port .in the cylinder which communicates with the voutlet andJis v'normally closed by the piston, and a. balancing plunger in the conduit, which plunger is linked to the operating lever and is arranged to move in to the conduit on movement of the lever 'to reduce the outlet pressure, said 'piston then operating toppen said port to permit 0f the escape from the conduit of the pressure fluid displaced by the plunger.

y'7. A sender unit as claimed in claim 4, com- ,loading or said sect-md spring being equaI to that of the loading spring acting on the piston, a ba1` ancing plunger exposed to the pressure` iny the prising a second spring operating on the piston valve in oppositionvto its balancing spring, the

conduitand linked to the .operating leverLand serving to balance, in all positions thereofl the reaction exerted thereon by the balancing spring, and a second plunger; di posed in the rear end of the cylinder and linked-f said lever, the second plunger being of the same effective area as the piston valve, and the balancing spring being mounted in compression between said second. plunger and the piston valve.

' EDWARD DODSON. 

